Method for identifying the cylinder phase of an internal combustion multi-cylinder four stroke engine

ABSTRACT

Method for identifying cylinder phase in an engine with an ignition and/or injection system wherein each cylinder is individually controlled, and with a sensor cooperating with a rotary target having an indexing element indicating a reference cylinder upper dead center position. The method including the steps of generating, on the reference cylinder, a disturbance other than the interruption of the injection, the disturbance of a type capable of causing a change in the engine torque, detecting the engine torque change by a change in a signal representative of the gas torque, caused by the generation of the disturbance, establishing a relationship between the time of generation and the detection of its result on the engine torque so as to derive the reference cylinder phase at the time of generation of the disturbance, and thereafter the phase of the other cylinders. The method of the present invention being particularly useful for four stroke engines with sequential ignition and/or injection.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for recognizing or identifying thephase of the cylinders of a multi-cylinder four-stroke internalcombustion engine, of the type equipped with an ignition system and/orfuel injection system controlled individually for each cylinder, andcomprising a sensor, often called the crank angle sensor, which is fixedwith respect to the engine and detects the movement past it of at leastone position mark fixed on a rotary target which rotates integrally withthe engine crankshaft, to supply a signal indicating the passage of thepiston of a reference cylinder of the engine through a determinedposition, for example approximately 100° crank angle before top deadcenter (TDC) for this piston.

2. Description of the Prior Art

To optimize the operation of a four-stroke internal combustion engine,particularly for controlling a sequential ignition system and/or asequential multi-point fuel injection system of such an enginecorrectly, it is known that the phase of the cylinders of the engineneeds to be identified or recognized, that is to say that at everymoment during an engine cycle it is necessary to know the position ofeach of the various pistons of the engine as well as which phase orstroke of the engine cycle each of the various cylinders of this engineis performing, and in particular the passage of the pistons through theTDC position at the beginning of the induction phase, so that the momentat which fuel is to be injected can be defined with precision, and theirpassage through the TDC position at the beginning of thecombustion-expansion phase, so that ignition (the moment and energy ofignition) can be defined with precision if the internal combustionengine is a controlled-ignition engine.

In effect, in an electronic and multi-point fuel injection system, whichcomprises at least one injector per cylinder for injecting meteredamounts of fuel just upstream of the corresponding inlet valve orvalves, and in which the injectors are operated periodically and atleast once per engine cycle, sequential injection consists in operatingthe various injectors in turn and in a given order, so that the meteredamounts of fuel can be injected toward the cylinders in the mostfavorable conditions relative to the corresponding induction phases.Likewise, a sequential ignition system allows ignition to be commandedin turn and in a given order in the various cylinders under the bestconditions with respect to the corresponding combustion-expansionphases, that is to say, in practical terms, with an appropriate ignitionadvance, with respect to TDC, at the beginning of the correspondingcombustion-expansion phase, as a function of the operating conditions ofthe engine, and does so without simultaneously causing an unnecessaryand sometimes disturbing spark in another cylinder which is performingan engine stroke ill-suited to being fired.

Ignition systems and/or fuel injection systems of the sequential typefor internal combustion engines generally comprise an engine controlcomputer, which in particular manages ignition and fuel injection andwhich must, for this, always know which phase the cylinders are in sothat it can precisely monitor the way in which the engine cycle isoccurring in each of these cylinders so that the engine control computercan calculate and command the amount of fuel delivered by each injector,that is to say in actual fact the injection period, starting from adetermined moment, on the one hand, and so that the engine controlcomputer can calculate the moment of ignition and trigger it bycommanding a corresponding ignition coil, on the other hand.

On a rotating target, that rotates integrally with the engine crankshaftor flywheel, and generally consists of a ring gear whose teeth,distributed about the periphery of the ring, constitute marks formeasuring the rotational speed of the engine and the position of thecrankshaft, by traveling past a sensor, for example avariable-reluctance sensor fixed on the engine, it is known to positionat least one position mark which for example consists of a tooth and/ora gap which has a different width from the others, so that it forms aunique feature that can be distinguished from the other teeth and/orspaces which are uniformly distributed, so that regions with an angularposition that correspond to a determined phase in the stroke of thepistons can be identified on the ring gear. By moving past the fixedsensor, the position mark generates a distinctive signal each time thepistons of the engine pass through a known fixed position, and thisallows the engine control computer to calculate, among other things, themoments at which the various pistons pass through top dead center.

However, in a four-stroke internal combustion engine, one engine cyclecorresponds to two revolutions of the crankshaft, which means that thepiston of the reference cylinder during each engine cycle passes throughTDC twice, but during two different phases of the engine cycle.

In particular, for engines with four in-line cylinders, numbered in turnfrom 1 to 4 from one end of the engine block to the other, the firingorder for the cylinders is generally given by the sequence 1, 3, 4, 2and the pistons of cylinders 1 and 4 pass simultaneously through topdead center alternately, one at the beginning of an induction phase andthe other at the beginning of a combustion-expansion phase, while thepistons of cylinders 2 and 3 also pass simultaneously through TDC with aphase shift of half of an engine revolution as compared with cylinders 1and 4, and like the latter cylinders alternately at the beginning of aninduction phase and at the beginning of a combustion-expansion phase.

In consequence, it is known that it is not possible simultaneously toobtain information regarding the angular position and informationregarding the phase of the various pistons of a four-stroke engine justusing the signals resulting from the passage of position marks on a ringgear driven with the crankshaft past a sensor fixed on the engine, thatis to say just from the signals given by a crank angle sensor whichusually is also an engine speed sensor.

For appropriate control of a sequential ignition and/or sequentialinjection system, it is known to make use of additional informationrelating to the phase of the cylinders and which is given by a secondsensor, possibly of the same type as the first one, for example avariable-reluctance sensor, and which is sensitive to the movement pastit of marks, such as teeth, borne by a second rotary target, such as aring gear driven in rotation at a speed which is half that of thecrankshaft, so that this second target makes one full revolution perengine cycle. For this, it is known to make the second target rotateintegrally with the distributor rotor shaft or, more frequently, thecamshaft or its drive pulley. It is especially known for the secondrotary target, driven with the camshaft, to bear a single position markwhich interacts with the second sensor to deliver a signal that has twologic levels.

Thus, the interaction of the first sensor with the first rotary targetgives the information on the angular position of the piston of areference cylinder, while the interaction of the second sensor and thesecond target gives the information regarding the phase of thisreference cylinder, for which reason the assembly formed by the secondsensor and the second rotary target is generally dubbed engine-phasesensor.

However, the presence of two sensors and two rotary targets is a factorin increasing the cost and the size and the complexity of assembly.

In order to overcome these drawbacks, FR-A-2 692 623 proposes a methodfor identifying the cylinders which saves on having to have an enginephase sensor and replaces it with an analysis of engine torque, in orderto detect misfires that are the result of a command to stop injectingfuel into a reference cylinder as the piston of this cylinder passesthrough TDC.

More specifically, this method for producing a signal for identifyingthe cylinders, comprises the following steps:

stopping injecting fuel for a given reference cylinder of the engine ata precise moment and for a precise length of time;

observing, using the signal for detecting misfires, the occurrence of amisfire in the reference cylinder following the non-injection and themoment that the misfire is detected;

calculating the number of TDCs separating the moment that injection isstopped in the reference cylinder and the moment the misfire resultingfrom this stoppage is detected, and identifying by deducing the momentof passage through TDC whether the reference cylinder is an induction ora power stroke; and

formulating the cylinder identification signal, this signal, which is inphase with the TDC signal, being reset at the moment that the referencecylinder passes through TDC on an induction or power stroke and takingup the successive order of combustion in the cylinders.

This method does however have the drawback that to use it assumes thepresence not only of a crank angle sensor, for identifying the passagethrough TDC of the piston of a reference cylinder, but also of a systemfor detecting misfires, capable of supplying a signal allowing misfiresthat occur in the various cylinders to be identified.

Another drawback with this method is that it can only be used on anengine that is equipped with a fuel injection system controlledindividually per cylinder, which means that it cannot be used on anengine equipped, for example, with a mono-point fuel injection systemand a sequential ignition system.

The problem underlying the invention is that of overcoming the drawbacksof the method known from FR-A-2 692 623 and of proposing a method ofrecognizing the phase of the cylinders which can be employed on anengine that is equipped with a crank angle sensor, without a phasesensor or a system for detecting misfires, it being possible for theengine to have a fuel injection system that is controlled individuallyand/or an ignition system that is controlled individually per cylinder.Thus the method of recognizing the phase of the cylinders according tothe invention can be used whether the ignition is sequential and withany kind of injection, for example mono-point, multi-point "full-group"(i.e. simultaneous injection into all cylinders) or semi-sequential,symmetric or semi-sequential asymmetric, or sequential and phased oralternatively sequential and unphased, or whether the injection ismulti-point sequential and with any kind of ignition, for example staticor twin static (that is to say producing sparks in two cylinderssimultaneously for each engine half revolution).

BRIEF SUMMARY OF THE INVENTION

For this, the method according to the invention, for recognizing thephase of the cylinders of a multi-cylinder four-stroke internalcombustion engine equipped with an ignition system and/or fuel injectionsystem controlled individually for each cylinder, and comprising asensor to supply a signal making it possible to identify that the pistonof a reference cylinder of the engine is passing through a determinedposition, is characterized in that it comprises at least one cycle ofthe steps that consist:

in commanding, on said reference cylinder and at a given moment that isassociated with said piston of the reference cylinder passing throughsaid determined position, a disturbance other than complete stoppage ofcommand for the injection of fuel, and liable to cause variation in theengine torque,

in observing the engine torque and detecting a possible variation inengine torque as a result of said command for disturbance on saidreference cylinder, and in detecting the moment at which said variationin engine torque occurs or the absence of variation in engine torque,

in examining the relationship between said given moment at which thedisturbance is commanded and said detected moment that the variation inengine torque or said absence of variation in engine torque occurs, inorder to deduce from this which phase of the engine cycle said referencecylinder was in when it passed through said determined position, and

in recognizing the phase of all the cylinders of the engine on the basisof knowledge of the phase of the reference cylinder.

When the engine is equipped with an ignition system controlledindividually per cylinder, the cylinders with the same TDC are commandedsimultaneously from the moment the engine is started or from the timethat an event liable to cause knowledge of the cylinder phase to be lostis detected and right up until the phase of the cylinders is recognized,and commanding the disturbance of the method of the inventionadvantageously consists in commanding a variation in the ignitioncommand for the reference cylinder. This variation applied to theignition command may consist in modifying the ignition energy and/or inmodifying the moment of ignition, as compared with normal operation,that is to say normal ignition command. The change to the moment ofignition must be understood as meaning an increase or decrease in theignition advance or retard, to be applied to operating scenarios inwhich the moment at which ignition is commanded is before or after themoment that the piston of the cylinder in question passes through TDC atthe beginning of a combustion-expansion phase.

By contrast, if the engine is equipped with a fuel injection systemcontrolled individually per cylinder, the method of the invention isadvantageously such that commanding the disturbance consists incommanding a modification to the injection period for the referencecylinder, the expression "changing the injection period" having to beunderstood as meaning an increase or a decrease in this period, withouthowever it being decreased so much that it completely cuts offinjection.

Advantageously too, the method of the invention consists in observingthe engine torque and in detecting its variations by observing anddetecting variations in a signal that represents the value of the gastorque generated by each combustion in each of the cylinders of theengine.

As a preference, in this case, the method is used on an engine in whichthe rotary target is a ring gear integral with the flywheel orcrankshaft of the engine, and whose teeth spread about its peripheryconstitute measurement marks, for which said position mark, which formsa unique feature on the ring gear constitutes a reference that indexesthe measurement marks per flywheel or crankshaft revolution, the sensorwhich is fixed with respect to the engine being a sensor that senses themarks moving past it and which is mounted close to the ring gear so thatit is advantageously possible, as known from FR-A-2 681 425, to delivera signal that represents the gas torque on the basis of the period,speed and variation in speed at which the marks move past the sensor,thanks to the logic-type torque sensor described in the aforementionedpatent.

To make it easier to determine the phase of the reference cylinder, themethod advantageously consists in examining the relationship between thegiven moment of commanding a disturbance and the detected moment thatthe variation in engine torque or the absence of variation in enginetorque occurs, by calculating the number of times that the piston of thereference cylinder passes through TDC between said two moments orstarting from said given moment, and in comparing it with at least onepre-determined number that corresponds to a determined phase of thereference cylinder in the engine cycle, as the corresponding pistonpasses through said determined position.

The method of the invention may consist in carrying out at least onecycle of said phase recognition steps as soon as the engine is started,after at least the first time that the piston of the reference cylinderpasses through said determined position or, on the contrary, in notcarrying out at least one cycle of said phase recognition steps untilafter a predetermined whole number of engine cycles counted from thefirst time that the piston of the reference cylinder passes through saiddetermined position, it furthermore being possible for the method toconsist in repeating, fairly periodically, at least one cycle of saidphase recognition steps in order to confirm or correct awareness of thephase of the cylinders.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Other advantages and features of the invention will emerge from thedescription given hereinbelow, without implied limitation, of theembodiments which are described with reference to the appended drawingsin which:

FIG. 1 is a diagrammatic view of a sequential ignition engine with itscrank angle sensor,

FIG. 2 is a diagrammatic side elevation of the crank angle sensor of theengine of FIG. 1,

FIGS. 3a, 3b, 3c, 3d are superimposed timing diagrams that respectivelyrepresent the signal from the sensor of FIGS. 1 and 2, the signals ofthe various pistons of the engine passing through TDC, and two possibledetections of variation in engine torque following a change in ignitionon one of the cylinders of the engine, and

FIGS. 4, 5 and 6a to 6d correspond respectively to FIGS. 1, 2 and 3a to3d for an engine with sequential injection, FIGS. 6c and 6d representingtwo possible detections of variation in engine torque following adisturbance in the injection for one of the engine cylinders.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, a controlled-ignition four-stroke engine with four in-linecylinders is depicted diagrammatically as M. Ignition in the cylindersof the engine M is provided by four ignition coils 1, 2, 3 and 4, eachof which corresponds to the cylinder (not depicted) with the same numberof the engine M. The ignition coils 1, 2, 3 and 4 are poweredsequentially with electric current, to provide ignition, by anelectronic engine control unit 6 which in particular also controls theinjection of fuel to the cylinders of the engine M. As is known, thisengine control unit 6 in particular acts as a computer and contains oneor more read-and-write memories, one or more read-only memories and atleast one processing unit produced in the form of a microprocessor ormicrocontroller. The engine control unit 6 also has various input andoutput interfaces for, respectively, receiving input signals coming fromthe various sensors that sense operating parameters of the engine, so asto carry out operations, and delivering output signals intended inparticular for the fuel injectors (not depicted) and the ignition coils1, 2, 3 and 4.

Conventionally, a firing sequence for the cylinders is in the followingorder: 1, 3, 4, 2.

The input signals of the engine control unit 6 include pulses deliveredby a variable-reluctance sensor 7 fixed to the block of the engine M andmounted facing and close to a ring gear 8 that rotates integrally withthe flywheel. At its periphery, the ring gear 8 has uniformly spacedteeth 9 forming measurement marks, and a unique feature 10, whichconstitutes a mark for indexing the teeth 9 and a mark that identifiesthe crank angle of the engine and which, when it moves past the sensor7, makes the latter deliver to the unit 6 a signal that indicates thatthe pistons of cylinders 1 and 4 are simultaneously passing through TDC.In the known way, the sensor 7 is also sensitive to the teeth 9 and 10moving past it, so that it delivers pulses that are proportional to thefrequency with which the teeth move past, which means that the unit 6can formulate a signal regarding the rotational speed of the engine. Inaddition, and as explained hereinafter, the unit 6 can also formulate asignal that represents the gas torque generated, by each combustion ineach of the cylinders of the engine M, on the basis of the pulsesreceived from the sensor 7.

Ignition in the cylinders that pass simultaneously through TDC iscommanded simultaneously from the moment the engine starts or from thedetection of any event liable to bring about a loss of knowledge of thephase of the cylinders, until this phase is recognized using the methodnow described.

The method for recognizing or identifying the phase of the cylindersconsists in carrying out at least one cycle of the following steps. Asrepresented in FIG. 3a, when the engine control unit 6 receives thepulse 11 delivered by the sensor 7 and which corresponds to the pistonsof cylinders 1 and 4 passing through TDC, the unit 6 simultaneouslyoperates the coils 1 and 4 to cause ignition in cylinders 1 and 4 withdisturbed ignition in coil 1 as compared with normal ignition, at themoment of the TDC signal 12 in FIG. 3b. This disturbed ignition in coil1 may consist in altering the moment of ignition, that is to sayincreasing or reducing the ignition advance or retard normallycalculated by the engine control unit 6 as a function of the engineoperating conditions, or alternatively may consist in altering theignition energy as compared with that normally defined by the unit 6.FIG. 3c represents a signal 13 formulated by the unit 6 andcorresponding to a detected variation in the engine torque which occursless than 2 TDCs after the moment the ignition 12 is altered in coil 1,but as a consequence of commanding this ignition disturbance, and thismakes it possible to conclude that the variation in torque was generatedin the cylinder 1 and therefore that the piston in cylinder 1 was at TDCat the beginning of a combustion-expansion phase at the moment when theunit 6 commanded the disturbance in ignition for this cylinder. Thesignal 13 that bears witness to the variation in engine torque as aconsequence of the disturbance in ignition in coil 1 of one of the twocylinders whose pistons are at TDC at the moment of the disturbance is asignal formulated by the unit 6 on the basis of the observation anddetection of variations in the gas torque. Therefore the unit 6 containsthe device for measuring the torque of an internal combustion enginedescribed in French Patent FR 2 681 425 and uses the method described inthis patent, whose description is incorporated into this description asreference. This known device and this known method allow the formulationof a signal that represents the gas torque on the basis of the periods,speeds and variations in speed at which the teeth 9 of the ring gear 8travel past the sensor 7. For further detail, reference can be made toFrench Patent FR 2 681 425, and it will merely be restated that themethod according to this patent, to produce a value that represents themean gas torque Cg generated by each combustion of the gaseous mixturein the cylinders of an internal combustion engine, the engine being ofthe kind comprising:

measurement marks (the teeth 9) arranged on a ring gear 8 integral withthe flywheel or the crankshaft;

means (the unique feature 10) for defining a reference for indexing themarks (9) per flywheel or crankshaft revolution;

a sensor 7 that senses the movement past it of the marks 9, mountedfixed close to the ring gear 8; comprises the following essentialoperations:

the formulation of a primary value that represents the time taken d_(i)for each of the marks 9 to move past the sensor 7;

the processing of said primary value d_(i) to produce two secondaryvalues which respectively represent the mean angular velocity Ω_(m) ofthe marks 7 during a period of combustions in the engine M and theprojection EcosΦ, onto the phase reference line of the marks relating tothe angular combustion periods, of the alternating component E ofinstantaneous angular velocity Ω_(i) of the marks at the frequency ofthe combustions in the engine; and

combining these two secondary values according to a relationship:Cg=-a.Ω_(m).EcosΦ+b. Ω_(m) ² to thus obtain the desired value, the termsa and b being empirically-determined constants.

As an alternative, the engine torque may be observed and its variationas the result of commanding disturbance in the ignition in cylinder 1,chosen to be the reference cylinder, may be detected, and the momentthat this variation in engine torque occurs may be detected by observingand detecting variations in a gas torque signal represented byinformation of some nature other than that mentioned hereinabove, forexample using signals relating to the pressure in the combustionchambers.

If, as represented in FIG. 3d, and by contrast with FIG. 3c, no enginetorque variation signal is delivered through the monitoring of thechange in gas torque signal, as a consequence of the ignitiondisturbance commanded in coil 1, this means that this ignitiondisturbance was commanded when the piston in cylinder 1 was at TDC atthe beginning of an induction phase, and therefore that the piston incylinder 4, which was at TDC at the same time, was at the beginning of acombustion-expansion phase.

From this deduction, which results from examining the relationshipbetween the moment that the signal 13 relating to the occurrence of thevariation in engine torque was detected and the moment when thedisturbed ignition 12 was commanded, the phase of cylinders 1 and 4 thenthat of cylinders 2 and 3 can be deduced.

This examination of the relationship between the moment that theignition disturbance is commanded and the moment that its consequence onengine torque is detected can be achieved by comparing the number ofTDCs between these two moments against a predetermined threshold number,for example 2 TDCs, so that if the signal 13 of variation in enginetorque is detected less than two TDCs after the signal commanding thedisturbance in ignition 12, as is the case in FIG. 3c, it can be deducedtherefrom that the cylinder 1 was in the combustion-expansion phase,whereas if the number of TDCs that elapse after the disturbance 12 iscommanded exceeds 2 before a variation in engine torque is detected, asshown in FIG. 3d, it can be deduced from this that the cylinder 1 was inthe induction phase.

To avoid any ambiguity in the relationship between commanding adisturbance in the ignition in the coil and its consequence on thevariation in engine torque, the disturbance is commanded on the coil ofthe reference cylinder for a complete engine cycle.

One or more consecutive cycles of the phase recognition steps describedhereinabove can be carried out as soon as the engine is started, forexample after the piston in cylinder 1 passes for the first time or forthe first few times through TDC.

As an alternative, the cycle of phase recognition steps may be carriedout after the phase of starting up the engine, that is to say after apredetermined whole number of engine cycles, this number being counted,for example, starting from the first time that the piston in cylinder 1passes through TDC.

It is also possible, after at least one cycle of the phase recognitionsteps carried out as soon as the engine is started, for further cyclesof these recognition steps to be repeated fairly periodically afterengine-start-up so as to confirm or correct knowledge of the phase ofthe cylinders resulting from the previous cycle or cycles of recognitionsteps.

In FIG. 4, the engine M differs from the engine of FIG. 1 only in thatinstead of a sequential ignition system it comprises a sequentialmulti-point fuel injection system by means of which each of thecylinders 1 to 4 of the engine M is supplied with fuel by acorresponding injector 21, 22, 23 or 24 controlled by the engine controlunit 26, similar to the unit 6 in FIG. 1, and which also controlsignition, in any appropriate way. Like the unit 6, the engine controlunit 26 also formulates an engine rotational speed signal, a signal thatthe pistons of cylinders 1 and 4 are passing through TDC, and a signalthat represents the gas torque from pulses it receives from the sensor7, fixed, like in the previous example, to the engine M and able todetect the teeth 9 and the unique feature 10 of the ring gear 8 thatrotates with the crankshaft travelling past it, under the sameconditions as explained hereinabove. The engine control unit 26therefore also contains the device for measuring the torque of aninternal combustion engine that is the subject matter of French PatentFR 2 681 425 and uses the method described in this patent.

As is known, the unit 26 sequentially controls the moments at which theinjectors 21, 22, 23 and 24 open and the open periods of these injectorsso that metered amounts of fuel can be injected as a function of theoperating conditions of the engine M.

In this example, the phase recognition method comprises the followingsteps: first of all, on receipt of the signal 31 of FIG. 6a, whichcorresponds to the unique feature 10 moving past the sensor 7, and whichindicates the pistons of cylinders 1 and 4 passing through TDC, adisturbance in the control of the corresponding injector 21 iscommanded, for cylinder 1 which is chosen to be the reference cylinder,this disturbance consisting in an increase or decrease in the injectionperiod, without this being able to completely cut off the injection. Atthe same time, the engine control unit 26 commands static twin ignitionin cylinders 1 and 4. The engine torque is then observed to detect itsvariation as a result of the commanding of the injection disturbancereferenced as 32 in FIG. 6b, and the moment that this variation inengine torque occurred, as indicated by the gas torque variation signal33 of FIG. 6c, obtained less than 2 TDCs after the injection disturbancewas commanded on injector 21 is detected if the piston in cylinder 1 wasat TDC in an induction phase when the injection disturbance wascommanded. By contrast, if the variation in engine torque correspondingto the signal 34 indicating a variation in gas torque in FIG. 6d is notdetected until after 2 TDCs after the injection disturbance wascommanded 32 in injector 21, this indicates that the phase in cylinder 1at TDC when the injection disturbance was commanded was acombustion-expansion phase rather than an induction phase.

In this example too, examining the relationship between the given momentat which the disturbance was commanded and the detected moment that thevariation in engine torque occurred, through the variation in gastorque, is achieved by calculating the number of times the piston of thereference cylinder passes through TDC between the two moments, and bycomparing this number with at least one predetermined threshold numberin order to deduce from this the phase of the reference cylinder as itfirst passed through TDC in question and to know the phase of all thecylinders.

As in the previous example, all the cylinders of the engine can havetheir phase identified from knowledge of the phase of the referencecylinder, and the injection disturbance on injector 21 can be commandedduring a complete engine cycle. A phase recognition cycle can be carriedout as soon as the engine is started, or a certain number of enginecycles after this starting, and may possibly be repeated fairlyperiodically to confirm or correct the knowledge of the phase of thecylinders resulting from a prior phase-recognition cycle.

It is obvious that the example of FIGS. 1 to 3 can be applied to anengine equipped with an ignition system controlled individually percylinder, independently of the type of its injection system, just likethe example of FIGS. 4 to 6 can be applied to an engine equipped with afuel injection system controlled individually per cylinder,independently of the type of its ignition control system.

However, the method of the invention is advantageously applied toengines in which the ignition and injection systems are of thesequential type.

Finally, it should be noted that the phase recognition method describedwith reference to FIGS. 4 to 6 can be used on a diesel engine, thedisturbance command relating only to the injection of fuel into theselected reference cylinder.

I claim:
 1. A method for recognizing a phase of cylinders of amulti-cylinder four-stroke internal combustion engine equipped with atleast one of an ignition system and a fuel injection system, said atleast one an ignition system and a fuel system controlled individuallyfor each cylinder and comprising a sensor for supplying a signal whereinidentifying that a piston of a reference cylinder of the engine ispassing through a determined position is possible, said methodcomprising at least one cycle of steps comprising:commanding, on areference cylinder and at a given moment that is associated with apiston of said reference cylinder passing through a determined position,a disturbance causing variation in engine operation; observing theengine operation and detecting a variation in engine operation as aresult of said commanding for said disturbance on said referencecylinder, and detecting one of the moment at which said variation inengine operation occurs and an absence of variation in engine operation;examining a relationship between said given moment of commanding saiddisturbance and said detecting one of the moment that the variation inengine operation occurs and said absence of variation in engineoperation occurs, in order to deduce which phase of engine cycle saidreference cylinder was in as a phase of said reference cylinder whensaid reference cylinder passed through said determined position; andrecognizing a phase of all cylinders of the engine on a basis ofknowledge of said phase of said reference cylinder, wherein saidcommanding said disturbance comprises commanding a modification to atleast one of ignition energy and injection period as compared withnormal operation, other than completely stopping ignition command andinjection command, and wherein said detecting any variation in engineoperation as a result of said commanding comprises detecting anyvariation in engine torque and a moment that said variation in enginetorque occurred.
 2. The method according to claim 1, wherein cylinderswith substantially the same top dead center are commanded substantiallysimultaneously from a condition selected from the group consisting ofwhen the engine is started, a time that an event liable to causeknowledge of a cylinder phase to be lost is detected, and right up untilthe phase of the cylinders is recognized.
 3. The method according toclaim 1, comprising observing engine torque and detecting variations inengine torque by observing and detecting variations in a signal thatrepresents a value of gas torque generated by each combustion in eachcylinder of the engine.
 4. The method according to claim 3, for anengine in which a rotary target comprises a ring gear integral with atleast one of a ring gear flywheel and a crankshaft of the engine, andincluding teeth spread about a periphery comprising measurement marks,for which a position mark comprising a feature on the ring gear,comprises a reference that indexes said measurement marks per revolutionof said at least one of said flywheel and said crankshaft, wherein saidsensor is fixed on the engine and comprises a sensor that senses saidmeasurement marks moving past said sensor and which is mounted close tosaid ring gear, said method comprising delivering a signal thatrepresents gas torque on a basis of at least one member selected fromthe group consisting of periods, speeds and variations in speed at whichsaid measurement marks move past said sensor.
 5. The method according toclaim 1, comprising examining a relationship between said given momentof commanding a disturbance and said detecting one of the moment thatthe variation in engine operation occurs and said absence of variationin engine operation occurs by a procedure selected from the groupconsisting of calculating a number of times that the piston of thereference cylinder passes through TDC between said given moment and saiddetected moment, and starting from said given moment, comparing saidgiven moment with at least one predetermined number that corresponds toa determined phase of the reference cylinder in the engine cycle, as thecorresponding piston passes through said determined position.
 6. Themethod according to claim 1, comprising carrying out at least one cycleof phase recognition steps substantially as soon as the engine isstarted after said piston of said reference cylinder passes through saiddetermined position at least a first time.
 7. The method according toclaim 1, comprising delaying carrying out at least one cycle of phaserecognition steps until after a predetermined whole number of enginecycles counted from a first time that said piston of said referencecylinder passes through said determined position.
 8. The methodaccording to claim 1, comprising repeating at least one cycle of phaserecognition steps in order to determine a condition selected from thegroup consisting of confirming a phase of the cylinders and correctingawareness of a phase of the cylinders.
 9. The method according to claim1, comprising commanding said disturbance on said reference cylinderduring an engine cycle.